linux-kernel - Re: [PATCH v3 0/6] RTL8231 GPIO expander support

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CACRpkdYSMjDaRY2chbFyBTJ4jeAjPtXX3+VW7MHu-wH2QoAfPA@mail.gmail.com>
Date:   Tue, 1 Jun 2021 13:48:43 +0200
From:   Linus Walleij <linus.walleij@...aro.org>
To:     Michael Walle <michael@...le.cc>
Cc:     Andy Shevchenko <andy.shevchenko@...il.com>,
        Hans de Goede <hdegoede@...hat.com>,
        Sander Vanheule <sander@...nheule.net>,
        Andrew Lunn <andrew@...n.ch>, Pavel Machek <pavel@....cz>,
        Rob Herring <robh+dt@...nel.org>,
        Lee Jones <lee.jones@...aro.org>,
        Mark Brown <broonie@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J . Wysocki" <rafael@...nel.org>,
        Bartosz Golaszewski <bgolaszewski@...libre.com>,
        Linux LED Subsystem <linux-leds@...r.kernel.org>,
        devicetree <devicetree@...r.kernel.org>,
        "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 0/6] RTL8231 GPIO expander support

On Tue, Jun 1, 2021 at 1:41 PM Michael Walle <michael@...le.cc> wrote:
> Am 2021-06-01 12:51, schrieb Linus Walleij:
> > On Tue, Jun 1, 2021 at 12:18 PM Michael Walle <michael@...le.cc> wrote:
> >> Am 2021-06-01 11:59, schrieb Linus Walleij:
> >
> >> > Just regarding all registers/memory cells in a register page
> >> > as default volatile (which is what we do a lot of the time)
> >> > has its upsides: bugs like this doesn't happen.
> >>
> >> I don't think this is the bug here. If it is really a write-only
> >> register
> >> the problem is the read in RMW. Because reading the register will
> >> return
> >> the input value instead of the (previously written) output value.
> >
> > True that. Write and read semantics differ on the register.
> >
> > Volatile is used for this and some other things,
> > like for example interrupts being cleared when a register
> > is read so it is strictly read-once.
>
> Isn't that what precious is for?

I never figured that one out. But I assume you are right.

Proper regmap semantics documentation is forthcoming! ;)

Yours,
Linus Walleij